Foundrymen have long poured metal by: indexing a mold under a pouring vessel (e.g., ladle) so as to register the mold gate with the pouring spout of the vessel; opening a valve (e.g., stopper) for a predetermined time interval to discharge the metal into the gate; closing the valve when the mold is filled; indexing the filled mold out of the pouring zone; and indexing an empty mold into place beneath the spout to repeat the cycle. Such systems are relatively slow due to the time lost while indexing the molds. Moreover, mold conveyors for such systems are subjected to repetitive starting and stopping which causes significant wear and tear thereon tending to erode the precision with which the gates and spouts can be registered. Hence, frequent and costly maintenance is required to insure accurate and reliable performance of the mold conveyor.
Foundrymen found that casting rates could be increased if the molds were equipped with extended (i.e., much larger than the mouths of the gates) pouring basins and the molds moved continuously through the pouring zone. Under these circumstances the extended (i.e., elongated in the direction of mold movement) pouring basins acted like funnels to direct the melt into the mold's gate and runner system. This also eliminated the need for precision gate-spout alignment equipment. The pouring rate of this equipment (i.e., for a given mold) was limited by the rate at which the melt could be discharged through the spout and mold residence time or length of time the mold basin remained beneath the pouring spout. For all practical purposes mold residence time was determined by the speed of the mold conveyor. Fast moving conveyors reduced mold residence time and hence was useful only with molds having small cavities. Slower moving conveyors were needed for large cavity molds.
Foundrymen continued to seek ways to increase the amount of metal that could be poured in a given time and, at the same time, reduce the manpower required to pour the metal. To this end, highly sophisticated automatic equipment such as described in U.S. Pat. No. 3,977,461, issued Aug. 31, 1976, was developed, and included coupling a mobile ladle to a mold in a pouring station such that the mold and ladle move together during the pour and thereby assure adequate residence time. A plurality of ladles are provided and each ladle carries only as much melt as is needed to pour a single mold. Such equipment is extremely complex, expensive, and replaces existing casting lines in most foundries where it is used.